Shipwrecks are the nightmare we have forgotten - the price Britain paid for ruling the waves from an island surrounded by treacherous rocks. The result is a coastline that is home to the world's highest concentration of sunken ships. But shipwrecks also changed the course of British history, helped shape our national character and drove innovations in seafaring technology, as well as gripping our imagination. Maritime historian Dr Sam Willis looks at how and why the shipwreck came to loom so large in British history.